// Copyright 2013 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_ARM64_UTILS_ARM64_H_
#define V8_ARM64_UTILS_ARM64_H_

#include <cmath>

#include "src/arm64/constants-arm64.h"
#include "src/utils.h"

namespace v8 {
namespace internal {

    // These are global assumptions in v8.
    STATIC_ASSERT((static_cast<int32_t>(-1) >> 1) == -1);
    STATIC_ASSERT((static_cast<uint32_t>(-1) >> 1) == 0x7FFFFFFF);

    uint32_t float_sign(float val);
    uint32_t float_exp(float val);
    uint32_t float_mantissa(float val);
    uint32_t double_sign(double val);
    uint32_t double_exp(double val);
    uint64_t double_mantissa(double val);

    float float_pack(uint32_t sign, uint32_t exp, uint32_t mantissa);
    double double_pack(uint64_t sign, uint64_t exp, uint64_t mantissa);

    // An fpclassify() function for 16-bit half-precision floats.
    int float16classify(float16 value);

    // Bit counting.
    int CountLeadingZeros(uint64_t value, int width);
    int CountLeadingSignBits(int64_t value, int width);
    V8_EXPORT_PRIVATE int CountTrailingZeros(uint64_t value, int width);
    V8_EXPORT_PRIVATE int CountSetBits(uint64_t value, int width);
    int LowestSetBitPosition(uint64_t value);
    int HighestSetBitPosition(uint64_t value);
    uint64_t LargestPowerOf2Divisor(uint64_t value);
    int MaskToBit(uint64_t mask);

    template <typename T>
    T ReverseBytes(T value, int block_bytes_log2)
    {
        DCHECK((sizeof(value) == 4) || (sizeof(value) == 8));
        DCHECK((1ULL << block_bytes_log2) <= sizeof(value));
        // Split the 64-bit value into an 8-bit array, where b[0] is the least
        // significant byte, and b[7] is the most significant.
        uint8_t bytes[8];
        uint64_t mask = 0xff00000000000000;
        for (int i = 7; i >= 0; i--) {
            bytes[i] = (static_cast<uint64_t>(value) & mask) >> (i * 8);
            mask >>= 8;
        }

        // Permutation tables for REV instructions.
        //  permute_table[0] is used by REV16_x, REV16_w
        //  permute_table[1] is used by REV32_x, REV_w
        //  permute_table[2] is used by REV_x
        DCHECK((0 < block_bytes_log2) && (block_bytes_log2 < 4));
        static const uint8_t permute_table[3][8] = { { 6, 7, 4, 5, 2, 3, 0, 1 },
            { 4, 5, 6, 7, 0, 1, 2, 3 },
            { 0, 1, 2, 3, 4, 5, 6, 7 } };
        T result = 0;
        for (int i = 0; i < 8; i++) {
            result <<= 8;
            result |= bytes[permute_table[block_bytes_log2 - 1][i]];
        }
        return result;
    }

    // NaN tests.
    inline bool IsSignallingNaN(double num)
    {
        uint64_t raw = bit_cast<uint64_t>(num);
        if (/*std::*/isnan(num) && ((raw & kDQuietNanMask) == 0)) {
            return true;
        }
        return false;
    }

    inline bool IsSignallingNaN(float num)
    {
        uint32_t raw = bit_cast<uint32_t>(num);
        if (/*std::*/isnan(num) && ((raw & kSQuietNanMask) == 0)) {
            return true;
        }
        return false;
    }

    inline bool IsSignallingNaN(float16 num)
    {
        const uint16_t kFP16QuietNaNMask = 0x0200;
        return (float16classify(num) == FP_NAN) && ((num & kFP16QuietNaNMask) == 0);
    }

    template <typename T>
    inline bool IsQuietNaN(T num)
    {
        return /*std::*/isnan(num) && !IsSignallingNaN(num);
    }

    // Convert the NaN in 'num' to a quiet NaN.
    inline double ToQuietNaN(double num)
    {
        DCHECK(/*std::*/isnan(num));
        return bit_cast<double>(bit_cast<uint64_t>(num) | kDQuietNanMask);
    }

    inline float ToQuietNaN(float num)
    {
        DCHECK(/*std::*/isnan(num));
        return bit_cast<float>(bit_cast<uint32_t>(num) | static_cast<uint32_t>(kSQuietNanMask));
    }

    // Fused multiply-add.
    inline double FusedMultiplyAdd(double op1, double op2, double a)
    {
        return fma(op1, op2, a);
    }

    inline float FusedMultiplyAdd(float op1, float op2, float a)
    {
        return fmaf(op1, op2, a);
    }

} // namespace internal
} // namespace v8

#endif // V8_ARM64_UTILS_ARM64_H_
